The present invention relates generally to means for sealing relative reciprocating members; more particularly, to means for preventing the flow of excess oil along the stem of a valve into a combustion chamber of an internal combustion engine, and specifically, to seals commonly known as valve stem seals.
Internal combustion engines have a plurality of intake and exhaust valves, each comprising a valve head and a stem reciprocally mounted in a valve guide. The valve guide may be an integral part of the cylinder head or block, or may comprise a separate member fitted into the cylinder head or block. The end of the valve stem most remote from the cylinder block is usually engaged by a rocker arm in an overhead valve engine or by a plunger in an L-configured engine. Both the rocker arm and the plunger are cam operated.
Oil is usually supplied to the upper end of the valve stem through an oil splash system or by a localized system through the rocker arm to the point of contact with the end of the valve stem so that the oil runs along the stem to lubricate the stem as it reciprocates within the guide.
As wear occurs in the valve guide or the valve stem, excess oil tends to work through the guide to the head of the valve where it may be drawn either into the combustion chamber, in the case of an intake valve, or through the exhaust port, in the case of an exhaust valve, leading, in either case, to an excess consumption of oil and formation of carbon deposits.
Valve stem seals made of various elastomers have been known for some time, several examples being shown in U.S. Pat. Nos. 3,498,621, 4,125,265 and 4,317,436. Such valve stem seals typically include a one-piece elastomeric member which fits around and on top of the valve stem guide. The one-piece elastomeric member of these valve stems is held in place by a biasing means and the sealing portion of the elastomeric member, which encircles the valve stem, is held in a hugging relationship with the stem by another biasing means.
Alternatively, some conventional valve stem seals have combined retaining means for securing the elastomeric member on top of the valve guide in combination with biasing means for the elastomeric member. Basically, all known embodiments of these prior valve stem seals suffer from the utilization of excessive amounts of expensive elastomeric material in their structure.
Accordingly, there is a need for a valve stem seal which not only can achieve the required performance parameters for oil consumption and wear resistance over the working life of the vehicle engine, but can also be made less expensive by reducing the amount of expensive elastomeric material required in the seals while retaining the superior performance parameters and wear characteristics required in internal combustion engines.